chapter 17 software testing - software engineering @ rit

These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e (McGraw-Hill 2009). Slides copyright 2009 by Roger Pressman. 1

Chapter 17

� Software Testing Strategies

Slide Set to accompany

Software Engineering: A Practitioner’s Approach, 7/eby Roger S. Pressman

Slides copyright © 1996, 2001, 2005, 2009 by Roger S. Pressman

For non-profit educational use only

May be reproduced ONLY for student use at the university level when used in conjunction with Software Engineering: A Practitioner's Approach, 7/e. Any other reproduction or use is prohibited without the express written permission of the author.

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Software Testing

Testing is the process of exercising a program with the specific intent of finding errors prior to delivery to the end user.


What Testing Showserrorserrors

requirements conformancerequirements conformance

performanceperformance

an indicationan indicationof qualityof quality


Strategic Approach� To perform effective testing, you should conduct

effective technical reviews. By doing this, many errors will be eliminated before testing commences.

� Testing begins at the component level and works "outward" toward the integration of the entire computer-based system.

� Different testing techniques are appropriate for different software engineering approaches and at different points in time.

� Testing is conducted by the developer of the software and (for large projects) an independent test group.

� Testing and debugging are different activities, but debugging must be accommodated in any testing strategy.


V & V

� Verification refers to the set of tasks that ensure that software correctly implements a specific function.

� Validation refers to a different set of tasks that ensure that the software that has been built is traceable to customer requirements. Boehm [Boe81] states this another way: � Verification: "Are we building the product right?" � Validation: "Are we building the right product?"


Who Tests the Software?

developerdeveloper independent testerindependent tester

Understands the system Understands the system

but, will test "gently"but, will test "gently"

and, is driven by "delivery"and, is driven by "delivery"

Must learn about the system,Must learn about the system,but, will attempt to break itbut, will attempt to break it

and, is driven by qualityand, is driven by quality


Testing Strategy

System engineering

Analysis modeling

Design modeling

Code generation Unit test

Integration test

Validation test

System test


Testing Strategy� We begin by ‘testing-in-the-small’ and move

toward ‘testing-in-the-large’� For conventional software

� The module (component) is our initial focus

� Integration of modules follows

� For OO software� our focus when “testing in the small” changes from

an individual module (the conventional view) to an OO class that encompasses attributes and operations and implies communication and collaboration


Strategic Issues� Specify product requirements in a quantifiable manner

long before testing commences. � State testing objectives explicitly. � Understand the users of the software and develop a

profile for each user category.� Develop a testing plan that emphasizes “rapid cycle

testing.”� Build “robust” software that is designed to test itself� Use effective technical reviews as a filter prior to testing� Conduct technical reviews to assess the test strategy

and test cases themselves. � Develop a continuous improvement approach for the

testing process.


Unit Testing

modulemoduleto beto be

testedtested

test casestest cases

resultsresults

softwaresoftwareengineerengineer


Unit Testing

interface interface

local data structureslocal data structures

boundary conditionsboundary conditionsindependent pathsindependent pathserror handling pathserror handling paths

modulemoduleto beto be

testedtested



Unit Test Environment

ModuleModule

stubstub stubstub

driverdriver

RESULTSRESULTS

interface interface

local data structureslocal data structures

boundary conditionsboundary conditions

independent pathsindependent paths

error handling pathserror handling paths



Integration Testing StrategiesOptions:Options:

•• the the ““ big bangbig bang ”” approachapproach•• an incremental construction strategyan incremental construction strategy


Top Down Integration

top module is tested with top module is tested with stubsstubs

stubs are replaced one at stubs are replaced one at a time, "depth first"a time, "depth first"

as new modules are integrated, as new modules are integrated, some subset of tests is resome subset of tests is re --runrun

AA

BB

CC

DD EE

FF GG


Bottom-Up Integration

drivers are replaced one at a drivers are replaced one at a time, "depth first"time, "depth first"

worker modules are grouped into worker modules are grouped into builds and integratedbuilds and integrated

AA

BB

CC

DD EE

FF GG

clustercluster


Sandwich Testing

Top modules areTop modules aretested with stubstested with stubs

Worker modules are grouped into Worker modules are grouped into builds and integratedbuilds and integrated

AA

BB

CC

DD EE

FF GG

clustercluster


Regression Testing� Regression testing is the re-execution of some subset of

tests that have already been conducted to ensure that changes have not propagated unintended side effects

� Whenever software is corrected, some aspect of the software configuration (the program, its documentation, or the data that support it) is changed.

� Regression testing helps to ensure that changes (due to testing or for other reasons) do not introduce unintended behavior or additional errors.

� Regression testing may be conducted manually, by re-executing a subset of all test cases or using automated capture/playback tools.


Smoke Testing� A common approach for creating “daily builds” for product

software� Smoke testing steps:

� Software components that have been translated into code are integrated into a “build.”

• A build includes all data files, libraries, reusable modules, and engineered components that are required to implement one or more product functions.

� A series of tests is designed to expose errors that will keep the build from properly performing its function.

• The intent should be to uncover “show stopper” errors that have the highest likelihood of throwing the software project behind schedule.

� The build is integrated with other builds and the entire product (in its current form) is smoke tested daily.

• The integration approach may be top down or bottom up.


Object-Oriented Testing� begins by evaluating the correctness and

consistency of the analysis and design models� testing strategy changes

� the concept of the ‘unit’ broadens due to encapsulation

� integration focuses on classes and their execution across a ‘thread’ or in the context of a usage scenario

� validation uses conventional black box methods

� test case design draws on conventional methods, but also encompasses special features


Broadening the View of “Testing”

It can be argued that the review of OO analysis and It can be argued that the review of OO analysis and design models is especially useful because the design models is especially useful because the same semantic constructs (e.g., classes, attributes, same semantic constructs (e.g., classes, attributes, operations, messages) appear at the analysis, operations, messages) appear at the analysis, design, and code level. Therefore, a problem in the design, and code level. Therefore, a problem in the definition of class attributes that is uncovered definition of class attributes that is uncovered during analysis will circumvent side effects that during analysis will circumvent side effects that might occur if the problem were not discovered might occur if the problem were not discovered until design or code (or even the next iteration of until design or code (or even the next iteration of analysis). analysis).


OO Testing Strategy� class testing is the equivalent of unit testing

� operations within the class are tested

� the state behavior of the class is examined

� integration applied three different strategies� thread-based testing—integrates the set of

classes required to respond to one input or event� use-based testing—integrates the set of classes

required to respond to one use case

� cluster testing—integrates the set of classes required to demonstrate one collaboration


WebApp Testing - I

� The content model for the WebApp is reviewed to uncover errors.

� The interface model is reviewed to ensure that all use cases can be accommodated.

� The design model for the WebApp is reviewed to uncover navigation errors.

� The user interface is tested to uncover errors in presentation and/or navigation mechanics.

� Each functional component is unit tested.


WebApp Testing - II� Navigation throughout the architecture is tested. � The WebApp is implemented in a variety of different

environmental configurations and is tested for compatibility with each configuration.

� Security tests are conducted in an attempt to exploit vulnerabilities in the WebApp or within its environment.

� Performance tests are conducted.� The WebApp is tested by a controlled and monitored

population of end-users. The results of their interaction with the system are evaluated for content and navigation errors, usability concerns, compatibility concerns, and WebApp reliability and performance.


High Order Testing� Validation testing

� Focus is on software requirements

� System testing� Focus is on system integration

� Alpha/Beta testing� Focus is on customer usage

� Recovery testing� forces the software to fail in a variety of ways and verifies that recovery is

properly performed

� Security testing� verifies that protection mechanisms built into a system will, in fact, protect it

from improper penetration

� Stress testing� executes a system in a manner that demands resources in abnormal quantity,

frequency, or volume

� Performance Testing� test the run-time performance of software within the context of an integrated

system


Debugging: A Diagnostic Process


The Debugging Process


Debugging Effort

time requiredtime requiredto diagnose theto diagnose thesymptom andsymptom anddetermine thedetermine thecausecause

time requiredtime requiredto correct the errorto correct the errorand conductand conductregression testsregression tests


Symptoms & Causes

symptomsymptomcausecause

symptom and cause may be symptom and cause may be geographically separated geographically separated

symptom may disappear when symptom may disappear when another problem is fixedanother problem is fixed

cause may be due to a cause may be due to a combination of noncombination of non --errors errors

cause may be due to a system cause may be due to a system or compiler erroror compiler error

cause may be due to cause may be due to assumptions that everyone assumptions that everyone believesbelieves

symptom may be intermittentsymptom may be intermittent


Consequences of Bugs

damage

mildannoying

disturbingserious

extremecatastrophic

infectious

Bug Type

Bug Categories:Bug Categories: functionfunction --related bugs, related bugs, systemsystem --related bugs, data bugs, coding bugs, related bugs, data bugs, coding bugs, design bugs, documentation bugs, standards design bugs, documentation bugs, standards violations, etc.violations, etc.


Debugging Techniques

brute force / testing

backtracking

induction

deduction


Correcting the Error� Is the cause of the bug reproduced in another part of the

program? In many situations, a program defect is caused by an erroneous pattern of logic that may be reproduced elsewhere.

� What "next bug" might be introduced by the fix I'm about to make? Before the correction is made, the source code (or, better, the design) should be evaluated to assess coupling of logic and data structures.

� What could we have done to prevent this bug in the first place?This question is the first step toward establishing a statistical software quality assurance approach. If you correct the process as well as the product, the bug will be removed from the current program and may be eliminated from all future programs.


Final Thoughts

� Think -- before you act to correct� Use tools to gain additional insight� If you’re at an impasse, get help from someone

else� Once you correct the bug, use regression

testing to uncover any side effects

chapter 17 software testing - software engineering @ rit

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